This invention relates to fireplaces, and more particularly to so-called fireplace forms which cause air from within a room to circulate over the back side of the firebox so as to be heated and then to be discharged back into the room.
Known fireplace forms include an enclosure or housing on the outside of and spaced from the sides, back, and top of a firebox so as to define a chamber between the firebox and the enclosure in which fresh air is heated. Typically, the enclosure has air inlets for the intake of air at its bottom and air outlets at its top for discharging the heated air. The outlets are often connected to appropriate air ducts for distribution of the heated air into a room. In many instances, natural convection within the chamber was sufficient to effect the circulation of air therewithin. In other instances, blowers have been utilized to aid in circulating the air. Reference may be made to U.S. Pat. No. 2,642,859 for disclosure of such a fireplace form. Other fireplace forms, such as are disclosed in U.S. Pat. No. 252,064 were intended for use in down-draft fireplaces. Down-draft fireplaces, however, are not widely used in residential fireplaces.
In other known fireplace forms, attempts have been made to increase the heating efficiency of the fireplace by circulating air through so-called "heat flues." Reference may be made to such U.S. Pat. Nos. as 2,165,661, 2,331,178 and 2,549,365 for examples of such fireplace forms with increased heat transfer abilities. Generally, these prior art fireplace forms did increase the thermal efficiency of the fireplace, but still a significant part of, if not the majority of, heat from the fire was wasted.